Wireless networks such as Enhanced UMTS, 802.16e and the like are being designed to support the packet switched (PS) domain only. Traditionally the user equipment, also known as a mobile station or mobile is either in active state with a dedicated connection or in paging or dormant state (i.e. sleep mode). In paging state the mobile supports discontinuous reception wherein the mobile sleeps and wakes up at pre-determined intervals to check if the network has paged it. In 3GPP (UMTS) the mobile has an additional CELL_FACH state where it continuously monitors the downlink common control channel for activity.
The paging state helps to conserve battery charge by reducing the average current drain, however at the cost of some latency for downlink transmissions. The mobile can at any time send an uplink signaling message to indicate a need to transmit in the uplink. In CELL_FACH state the mobile is unable to conserve battery charge due to the continuous monitoring of the control channels.
One of the undesirable effects of the paging state is that there may be data that is to be exchanged with the mobile, however, when the mobile wakes at the predetermined time or frame, radio conditions are poor. It may also be possible that the mobile was in good conditions while it was in discontinuous reception (DRX) state, i.e. paging state, and the network was unable to communicate with the mobile. This has the undesirable result wherein data is exchanged in non-optimum radio conditions leading to the mobile being awake for a potentially longer time as a result of retransmission and in effect negating any potential battery savings. Therefore, it is desirable to be able to enter a sleep pattern that provides sufficient flexibility to the scheduler while simultaneously allowing the mobile to save battery whenever possible.
Moreover, while a mobile is in sleep mode, it is unable to communicate its channel conditions to the network until after wake-up. Thus the mobile may wake during undesirable channel conditions such that the mobile may not be able to communicate with the network or require multiple retransmissions to the network. In this case the mobiles wakes up and then goes back to sleep without any data exchange due to lack of sufficiently good channel conditions.
The various aspects, features and advantages of the present invention will become more fully apparent to those having ordinary skill in the art upon careful consideration of the following Detailed Description with the accompanying drawings described below.
Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of embodiments of the present invention.